Đáp án:
$\begin{array}{l}
A = \left( {x - 2} \right)\left( {{x^4} + 2{x^3} + 4{x^2} + 8x + 16} \right)\\
= \left( {3 - 2} \right).\left( {{3^4} + {{2.3}^3} + {{4.3}^2} + 8.3 + 16} \right)\\
= 211\\
B = \left( {x + 1} \right)\left( {{x^7} - {x^6} + {x^5} - {x^4} + {x^3} - {x^2} + x - 1} \right)\\
= \left( {x + 1} \right)\left( {x - 1} \right)\left( {{x^6} + {x^4} + {x^2} + 1} \right)\\
= \left( {{x^2} - 1} \right).\left( {{x^6} + {x^4} + {x^2} + 1} \right)\\
= \left( {{2^2} - 1} \right)\left( {{2^6} + {2^4} + {2^2} + 1} \right)\\
= 255\\
c)C = \left( {x + 1} \right)\left( {{x^6} - {x^5} + {x^4} - {x^3} + {x^2} - x + 1} \right)\\
= \left( {2 + 1} \right)\left( {{2^6} - {2^5} + {2^4} - {2^3} + {2^2} - 2 + 1} \right)\\
= 3.43\\
= 129\\
d)D = 2x\left( {10{x^2} - 5x - 2} \right) - 5x\left( {4{x^2} - 2x - 1} \right)\\
= 20{x^3} - 10{x^2} - 4x - 20{x^3} + 10{x^2} + 5x\\
= x\\
= - 5
\end{array}$
